1. Field of the Invention
This invention relates to insulated building boards having a fire-resistant cementitious coating composition and compositions and methods for making the same.
2. Description of the Prior Art
Cementitious compositions comprised of portland cement and from 30-55% by weight of cenospheres (cellular glass particles derived from flyash) are disclosed in British Patent No. 1,514,239. In that patent, the portland cement-cenosphere composition are formed into a slurry with water and the mixture together with glass fibers is sprayed on a vacuum bed mold surface followed by dewatering to form a sheet which is then removed and left to cure and dry. That patent also discloses the impregnation of the dry, but partially cured sheet, by monomers and catalysts followed by heating to effect polymerization of the monomer. Methylmethacrylate is disclosed as a particularly useful monomer for this purpose.
The use of cenospheres in flexible polymeric polyurethane foams is disclosed in U.S. Pat. No. 3,917,547 patented Nov. 4, 1975. In that patent, polyurethane or other flexible foams are blended with flyash containing a substantial amount of cenospheres which are present in the composition in amounts of from between about 5 and 75% by volume.